Pure fluid logic element



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[WEI/7W5 EDWIN R. PHILLIPS TREVOR D. READER AT T ORNE Y5 United StatesPatent 3,405,736 PURE FLUID LOGIC ELEMENT Trevor D. Reader, King ofPrussia, and Edwin R. Phillips, Rosemont, Pa., assignors to Sperry RandCorporation, New York, N .Y., a corporation of Delaware Filed Oct. 13,1964, Ser. No. 403,586 3 Claims. (Cl. 13781.5)

The present invention generally relates to a pure fluid logic element,and more particularly, to a pure fluid inverter having a relatively highpower gain.

In pure fluid technology, it is well known that a fluid power stream jetof realtively high energy may be deflected through a small acute anglewithout losing its integrity by the application thereto of a controlfluid jet of lesser energy, generally at a right angle in order toprovide maximum deflection per unit of control stream energy. This isthe well known stream interaction or momentum exchange type amplifier.Prior art fluid logic elements as, for example, inverters have beenbuilt using this approach, i.e., the power fluid jet, when present byitself, is recovered in an output channel leading to some utilizationdevice whereas, with the application of control signal fluid, said powerjet is deflected away from the output recovery channel so that no fluidsignal is directed to said utilization means. The power gain here isinversely proportional to the energy of the control stream necessary todeflect the power stream jet to a degree where the latter is completelyremoved from the output recovery channel. Since greater control streamenergy is necessary for larger values of power stream deflection, therequirement in such a momentum exchange inverter to completely switchpower stream flow away from the output recovery channel thereby lowersthe gain of the unit to a value where it is not too attractive.

' The present invention in one aspect thereof reduces, if not completelyobviates, the difiiculties leading to rela tively low gain of prior artmomentum exchange inverters by placing an attraction wall near the powerstream jet on the side opposite the control signal jet, This wall, byvirtue of its positioning and dimension, permits the creation of a lowpressure boundary layer almost as soon as power stream deflectioncommences which then acts as an aid to further power stream deflectionwithout, however, subsequently causing any permanent or stable powerstream lockon to the attraction wall in the absence of a control stream.Thus, only as the power stream begins its deflection away from theoutput recovery channel (in response to an impinging control stream) issaid boundary layer formed to thereby assist the control stream incompleting power stream deflection to the maximum degree whereby nofluid is directed to the utilization means. Upon termination of theimpinging control stream, this wall attraction is insuflicient tomaintain this large power stream deflection, such that the power streamnow swings back towards its normal, undeflected path. In so doing, thisreduces and then finally destroys whatever boundary layer had beenpresent during the presence of the control stream. Thus, the same degreeor amount of power stream deflection as obtained in prior art momentumexchange inverters can be provided in the present device by a controlstream of lesser energy so as to result in higher gain.

Therefore one object of the invention is to provide a novel pure fluidlogic element which employs an attraction wall adjacent the deflectedpath of a fluid power stream in order to increase the gain of the unit.

Another object of the present invention is to provide a pure fluidinverter with an attraction wall therein in such a position as to avoidany permanent lockon of the power stream thereto.

In order to further insure non-stable boundary layer adhesion of thepower stream along the attraction wall and to provide for a quick returnof the power stream at the termination of the control signal, anadditional novel feature of the invention is the use of means providingconstant communication of the boundary layer region with a source offluid whose static pressure is such as to rapidly dissipate the lowpressure boundary layer during the swing back of the power stream awayfrom the attraction wall. This source of fluid further acts, at least inone of the embodiments of the invention, as a base reference point onone side of the power stream against which a control static pressuresignal operates on the opposite side of the power stream in order toselectively cause deflection thereof. Furthermore, second means can alsobe provided for communication of the opposite side of the power streamwith said source of fluid in order to prevent the formation of anytransverse pressure gradient across the power stream due to causes otherthan control signal ac tivity or the boundary layer region adjacent theattraction wall.

Therefore a further object of the present invention is to provide afluid logic unit with an attraction wall, wherein there is constantcommunication of one or both sides of the power stream with a source offluid at a fixed pressure.

One embodiment of the present invention uses a control fluid jet toprovide power stream deflection by virtue of momentum exchange, whereasanother embodiment employs a fluid static pressure cushion appliedagainst a relatively long length of the moving power stream. Theparticular advantage of using said static pressure, rather than thedynamic or kinetic pressure of a moving controljet, is that it permitsthe power stream to deflect through a greater angle with less controlpower being required. This novel static pressure control also is of usein other types of pure fluid amplifiers apart from particularembodiments herein with the attraction Wall.

Therefore, another object of the invention is to provide a fluidamplifier unit which includes control means for providing a body orcushion of static pressure fluid as the power stream deflecting agent.

These and other objects of the present invention will become apparentduring the course of the following description to be read in view of thedrawings, in which:

FIGURE 1 is a plan view in section of a first embodiment of the presentinvention which employs a control jet for power stream deflection;

FIGURE 2 is a diagrammatic enlarged view of the critical dimensions ofthe attraction wall used in obtaining high gain; and

FIGURE 3 is a second embodiment of the present invention which employsmeans for applying control fluid static pressure against the power jet.

FIGURE 1 shows a first embodiment of the novel inverting element whichuses the basic principle of an attraction wall in order to enhance itsgain. A block or body 10 of fluid impervious material, which can bemetal, plastic, or the like, has cut or otherwise formed therein aplurality of interconnected fluid channels and chambers, preferably ofrectangular cross-section as is customary in the art. In particular, apower stream input channel 12 receives relatively high energy powerstream fluid from some source 14 via a connecting pipe 16, with saidpower stream input channel IZ'terminating in a nozzle orifice 18 locatedin one end of a fluid interaction chamber 20. At the opposite chamberend wall, a first power stream output channel 22 is located directly inline with power stream input channel 12, so that the normal undeflectedtrajectory of power stream fluid across chamber 20 will take it intooutput channel 22 from whence it is transferred via a pipe 24 to somefluid utilization means 26 (which in turn could be another pure fluidlogical element). The side walls of channel 22 need not and do notprovide any boundary layer lock on effect, since the flow energy of thepower stream is sufficient to establish this path through chamber 20.Also leaving the opposite end of chamber is a second power stream outputchannel 28 which makes an acute angle with output channel 22 and lies toone side of it at about the juncture of the chamber opposite end walland one chamber side wall. Channel 28, in the case of a pneumaticamplifier, usually exhausts into the surrounding lower pressureatmosphere which thus acts as a low pressure dump. However, where a gasor fluid other than air is employed, then the output of channel 28 canbe connected back to source 14 via a low pressure return manifold ordump. If the power stream fluid from nozzle 18 is deflected (by meanssubsequently to be described) from its normal undeviated path to a paththrough channel 28, the fluid normally applied to utilization means 26is discontinued for the length of time that the power stream deflectingmeans is in operation. In this way the inverting logical function isperformed. It would, of course, also be possible to further connectchannel 28 to some form of utilization means which responds to the powerstream in its deflected position.

The particular control means in FIGURE 1 for so deflecting the powerstream comprises at least one control stream input channel 30 whichreceives, via a pipe 32, control fluid from a selectively actuatedsource 34. The control channel 30 terminates in a nozzle orifice 36located in that side wall of chamber 20 which is opposite to the chamberside wall from which channel 28 branches. By selectively applying fluidto channel 30 from source 34, the channel static fluid pressure isconverted by nozzle 36 into a control fluid jet having primarily kineticenergy which issues forth into chamber 30 so as to strike the powerstream at about a right angle thereto. By virtue of momentum exchangebetween the control stream and power stream particles, the direction ofthe power stream is shifted right to cause flow through channel 28 andeventual exhaust to the low pressure dump. Normally, the angle of powerstream deflection is proportional to the energy of the control streamfluid. Since a fairly large angle of deflection is required in FIGURE 1in order to shift the power stream completely away from output channel22, it is seen that relatively large control stream energy (although notas large as the power stream energy) might thus be required, which inturn lowers the gain of the device since gain may be defined as theratio of the output utilization signal (power stream energy) to thecontrol signal energy required for negation of same. If channel 28 doesnot have any side wall in the direction of power stream deflection, orincludes such a side wall which is not strategically placed in themanner taught by the present invention, deflection of the power streamis due entirely to said stream interaction (momentum exchange) inchamber 20. However, in the present invention an attraction wall 38 isplaced near the deflected path of the power stream on the side oppositeto the control signal jet from orifice 36. Attraction wall 38 mayactually be an extension of the side wall of chamber 20 as it turns tofollow power stream output channel 28 to the point of exhaustion intothe low pressure dump. Also provided in FIGURE 1 is a cavity volume 40which separates the upstream end of wall 38 from the end wall of chamber20 in which orifice 18 is located. This cavity 40 is preferablypermanently connected to a source of static pressure fluid such as thelow pressure dump to which channel 28 is connected by means of a fluidcommunication channel 42, but this feature is not absolutely necessaryin the FIGURE 1 embodiment if the width of cavity 40 mouth along thepower stream axis is made sufficiently large. The communication ofcavity 40 with the low pressure dump permits a more rapid return of thepower stream from channel 28 to channel 22 at termination of controlstream activity, since the low pressure of the boundary layer along wall38 is quickly raised by addition of fluid via cavity 40 and channel 42once the entrainment ability of the power stream decreases as the switchback is in progress. Where channel 42 is employed, a second cavity 44 isalso preferably provided on the opposite side of chamber 20 at alocation downstream from control channel 30, with this cavity 44 beingin constant communication with the same source of fluid as is channel 42(illustrated to be the low pressure dump) by means of the large opening45 in body 10. Cavity 44 cooperates with cavity 40 and channel 42 inequalizing the static pressure across the power stream in chamber 20 soas to insure the absence of power stream lockon to the attraction wall38 due to causes other than presence of the control signal jet and/ orthe creation of the low pressure boundary layer region against wall 38.

FIGURE 2 is an expanded view of the chamber 20 vicinity in the FIGURE 1fluid amplifier. It is provided for the purpose of explaining thecritical dimensions of attraction wall 38, relative to other dimensionsof the amplifier, in order to provide a small boundary layer effect toenhance gain but without causing stable power stream flow in outputchannel 28. The three critical dimensions are shown in FIGURE 2 to bethe length A of attraction wall 38, the distance B of the upstream edgeof attraction wall 38 from the centerline of power stream nozzle 18, andwidth C of the cavity 40 mouth. These dimensions are adjusted relativeto one another and also to the power stream energy, such that anypredetermined degree of power stream deflection into channel 28thereafter causes a boundary layer effect between it and wall 38 so asto provide some attraction by said wall to the now deflected powerstream. Boundary layer effect may be defined as the entrainment of fluidby a flowing stream in a region between said stream and a side wall suchthat the pressure in said boundary layer region is reduced, thuspermitting the stream to be attracted toward the wall. Any such boundarylayer effect will obviously reduce the power or energy required of thecontrol stream flu-id in forcing the power stream completely intochannel 28. As more of the power stream flows through channel 28 andmoves closer to wall 38, its entrainment efi'iciency rises to therebyreduce the boundary layer pressure to an even greater extent which inturn increases the wall attraction effect aiding in the power streamdeflection. Consequently, by use of the attractive effect of wall 38,the required degree of power stream deflection can be procured in thepresent invention with less control stream energy than formerly requiredin prior art inverters, so as to result in an increase in gain. Restatedin a different way, the power stream is deflected by the control signalsuch that the closer the power stream gets to wall 38, the less power isnecessary from the control fluid because the now created boundary layeradjacent the wall itself aids in the power stream deflection. In otherwords, the wall shares in providing the total force necessary to keepthe power stream totally deflected into channel 28. However, wall 38must be positioned such that maximum boundary layer attraction offeredby it to the deflected power stream cannot maintain said power stream ina path through channel 28 during the absence of control signal input.That is to say, when control fluid source 34 subsequently becomesde-energized or de-activated so as to terminate the control fluid jetfrom nozzle 36 (or alternatively, at least reduced to have lesserenergy), the deflected power stream in channel 28 must now be able totear itself away from wall 38, thus weakening the boundary layerbecauseof less efficient power stream entrainment, and then return toits undeflected path through channel 22 at which time the boundary layeris completely destloyed. The attraction wall 38 is thus placed farenough away from the undeflected power jet to have no effect orinfluence thereon, and comes into play only when the power stream ismoved closer thereto by action of the control jet. For any given controlfluid energy, a position of wall 38 can be chosen to accomplish theabove described functions.

It has been found that the smaller the value B in FIG- URE 2, thegreater will be the effect of wall attraction on a deflected power jet.The larger dimension A is, the greater is the effect of said wallattraction, but a change in dimension A has a lesser effect than does achange in dimension B. A change in dimension C apparently produces thegreatest effect of changes in any of said three dimension. The smaller Cis, the greater the said wall attraction. 1

FIGURE 3 shows a second embodiment of the present invention which alsoemploys the basic feature of an attraction wall to obtain a gainincrease, but wherein the control signal applied against the powerstream jet is in the form of a fluid body having primarily staticpressure energy rather than a mass flow dynamic jet having primarilykinetic energy. .This additional feature will be described in subsequentparagraphs, but generally it may be said here that a control staticpressure signal applied over a relatively large power stream area alsopermits of greater power stream deflection with less control power beingrequired such that the attraction wall inverter of FIGURE 3 has evenhigher gain than does FIGURE 1. For this reason, too, the use of acontrol fluid pressure cushion in other types of fluid amplifier unitsis novel and useful because of the gain increase afforded thereby. TheFIGURE 3 embodiment is further capable of operating at very low Reynoldsnumbers and is responsive to short input pulse rise times. It alsopermits greater tolerances in element geometry. As inthe FIGURE 1embodiment, the pure fluid inverter of FIGURE 3 is comprised of a groupof interconnected fluid channels formed in a body 50 of fluid imperviousmaterial. A power stream input channel 52 and power stream source 54'are provided to produce a power stream jet of relatively large energywhich issues forth into a chamber 56 from a nozzle 58 formed in one endwall thereof. Leaving the opposite end wall of chamber 56, and directlyin line with channel 52, is a first power stream output channel 60 whichreceives the normally undeflected power stream jet and conveys same viapipe 62 to some utilization means 64. No boundary layer lockon effectneed be provided in channel 60. A second power stream output channel 66also leaves said opposite chamber end wall at an acute angle withchannel 60, with said channel 66 being separated from channel 60 by adivider edge 80 and further including an attraction wall 68 so locatedin the manner of FIGURE 1 to provide a boundary layer effect whichenhances gain for deflection of power stream fluid into said channel 66.A cavity 70 lies between the upstream edge of wall 68 and the nozzle endwall of chamber 56. Although distance B (between the upstream edge orcorner of said wall 68 and the power stream flow centerline) is shown tobe smaller than in the case of FIGURE 1, it should be noted that thewidth C of the cavity 70 mouth (measured along the power stream flowaxis) is larger so as to compensate for the smaller B dimension. Outputchannel 66 exhausts to a low pressure dump or return manifold hereillustrated to be the atmosphere in the case of a pneumatic inverter.

As has already been mentioned, a different form of fluid control signalis provided in FIGURE 3 from that shown in FIGURE 1. A large chamber 72is formed in the upstream portion of that side wall of chamber 56 whichis opposite to the side wall from which channel 66 branches. The mouth73 of said chamber 72 is considerably wider (as seen in the illustratedplan view) than the width of control nozzle 36 in FIGURE 1 so that itfronts along the power stream flow path through chamber 56 for a fairlylong distance, preferably greater than one-third of the chamber length.This makes the area of the power stream, which is exposed to controlfluid force, substantially greater in FIGURE 3 than the power streamarea against which the considerably smaller diameter control jet inFIGURE 1 impinges. A control fluid input channel 74 is supplied withfluid from a selectively aetuable control fluid source 76 via pipe 78 soas to fill chamber 72 with fluid to thereby increase the static pressuretherein without, however, causing any significant conversion of staticfluid pressure to dynamic or kinetic fluid pressure as is the case inchannel 30 and nozzle 36 of FIGURE 1. Consequently, a fluid control jet,as such, does not strike the power stream jet in FIGURE 3, but there israther a cushion of control fluid from chamber 72 bearing against thepower jet curtain created by nozzle 58. Although no specific means hasbeen hereinbefore described for use as the sources 34 (FIGURE 1) or 76of control fluid, one such input, among others, can come from the outputof fluid logical 'OR circuit such as the one disclosed in a pendingapplication S.N. 332,554, Fluid OR Gate, by Trevor D. Reader, now US.Patent 3,282,281. Since the control fluid in chamber 72 has little, ifany, velocity in the direction of chamber 58, there is no appreciableexchange of momentum between the control and power fluids. Cavity 70furthermore constantly communicates via an opening 71 in body 50, with asource of static pressure lower than the active signal presure inchamber 72. This last named source may in certain cases conveniently bethe same low pressure dump or return manifold to which channel 68 isconnected, as shown in FIGURE 3. Any increase in control fluid staticpressure at the mouth 73 of chamber 72 above the static fluid pressureexisting at the mouth of cavity 70 produces a transverse static pressuredifferential or gradient across the power stream as it issues fromnozzle 58, which in turn deflects said power stream away from channel 60and towards channel 66. As soon as some power stream fluid commences toflow in channel 66, a boundary layer region is created between it andwall 68. When there is suflicient power stream flow through channel 66,entertainment thereby of fluid in the boundary layer region adjacentwall 68 is at a faster rate than the rate at which fluid may be suppliedto said boundary layer region via cavity 70 from the source connected toopening 71. This causes said boundary layer static presure to be reducedbelow the cavity 70 pressure which thereupon aids the control fluidstatic pressure differential to further deflect the power streamcompletely into channel 66. Upon a subsequent and suflicient decrease inthe chamber 72 static pressure, as by termination of source 76 activityand withdrawal of fluid from chamber 72, the transverse fluid staticpressure differential across the power stream at the region of nozzle 58thereupon disappears. In order to almost immediately reduce to zero thistransverse control signal pressure gradient across the power stream atpractically the instant of termination of control source 76 activity,FIGURE 3 can, if desired, also be provided with an additional cavityleading from chamber 58 downstream from mouth 73 in the manner of cavity44 in FIGURE 1, with said additional cavity being connected to the samesource of fluid as is cavity 70, e.g., the low pressure dump to whichchannel 68 is also connected. The attractive effect exerted by theboundary layer region at wall 68 is by itself insufficient to maintainpower stream flow completely in channel 66 and the power stream nowbegins to switch back 'into channel 60 thus weakening the wallattraction force so that it has a decreasing effect upon the powerstream. As an additional aid to fast power stream return into channel68, the diminishing power stream entrainment in channel 68 finally failsto exhaust fluid from the boundary layer region faster than the rate atwhich fluid is being supplied to said region from cavity 70.Consequently, the low pressure boundary region very quickly disappearsso as to effect a rapid return of power stream flow into channel 60. Theparticular location of wall 68 relative to other parts of the unit, andthe communication of cavity 70 with a body of fluid for replenishingentrained fluid in the boundary layer region, therefore causes power jetfluid in channel 66 to quickly switch back into output channel 60 at theconclusion of control signal activity.

A further feature of FIGURE 3 is the provision of slightly divergingside walls in channel 66 such that said channel acts as a diffuser forpower stream flow therethrough. This in turn permits the static pressureat the channel 66 entrance (in the vicinity of divider edge 80) to belower than the normal quiescent or ambient static pressure existing atthe output of channel 60 in the absence of any power stream flow throughthe latter. This low channel 66 entrance pressure causes someentrainment, by the moving power stream fluid in channel 66, of thequiescent fluid standing in channel 60 so as to cause a small reversefluid flow in channel 60 in the direction of the dotted arrow. Thisreverse flow travels a path around edge 80 and into channel 66 foreventual exhaust into the low pressure dump, thereby causing the staticpressure at the channel 60 output to utilization means 64 to be slightlylower than the dump pressure. This reverse flow eifect makes even morepronounced the ditfe'rence between the two pressure levels which existat the output of channel 60 according to the presence or absence ofpower stream flow therethrough.

While several different embodiments of this invention have been shownand/or described, modifications may obviously be made thereto by thoseskilled in the art without departing from the novel principles definedin the appended claims.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A fluid inverter comprising; a body member having a fluid interactionchamber disposed therein, said interaction chamber having an end wall inwhich a fluid power nozzle is disposed, said fluid power nozzle beingadapted when subjected to fluid input pressure to project a power jetthrough the interaction chamber, an output duct positioned to receivethe undeflected power jet, said output duct comprising first and secondspaced apart wall members located down stream from the power nozzle andon opposite sides of the axis of the power nozzle, a control signalchamber having an input duct at one end thereof for receiving controlfluid input signals and a mouth portion at the other end thereof whichopens into the interaction chamber on the same side of the power nozzleas the first wall member of the output duct, the said mouth portionextending from the power nozzle to a point at least one third the lengthof the interaction chamber downstream from the power nozzle, saidcontrol signal chamber being operative so that when a control fluid isapplied thereto a static pressure signal will exist at said 8 mouthportion thereby to deflect the power jet away from said output duct, avent for said interaction chamber comprising the area between the saidend wall and the second of said wall members comprising said outputduct, and a divider block located in the 'said vent dividing said ventinto two unloaded vent channels the first vent channel of which isdefined by a first surface of said divider block and the said end walland the second vent channel of which'is' defined by a second surface ofsaid divider block and the second of said wall members of said outputduct; the second vent channel providing an exhaust path for the powerjet when it is deflected by a suitable pressure applied to the controlchamber, said second surface of said divider block forming an acuteangle with the axis of the power jet and being positioned anddimensioned to provide'a boundary layer attraction force for the powerjetonly when said power jet is in its deflected position, and said firstvent acting to reduce the boundary layer attraction force of the secondsurface of said divider block so that it is insufficient to maintainsaid power jet in its deflected position in the absence of a suit ablecontrol pressure applied to said control orifice.

2. The fluid inverter of claim 1 wherein the said twovent channelsexhaust into the same static low pressure dump.

3. The fluid inverter of claim 1 wherein said divider block is shaped toprovide the said one-vent channel with a cross sectional area ofexpanding size.

References Cited UNITED STATES PATENTS 3,001,539 9/1961 Hurvitz 137-8153,159,168 12/1964 Reader 137-815 3,187,762 6/1965 Norwood 137-81.53,204,652 9/1965 Bauer 137-815 3,208,463 9/1965 Hurvitz 137-8153,258,023 6/1966 Bowles 137-815 3,262,466 7/1966 Adams et al 137-8153,107,850 10/1963 Watten et a1 137-81.5 X 3,233,622 2/1966 Boothe137-815 3,275,013 9/1966 Colston 137-815 3,282,281 11/1966 Reader137-815 FOREIGN PATENTS 1,083,607 6/ 1960 Germany.

SAMUEL SCOTT, Primary Examiner.

U.S. DEPARTMENT OF COMMERCE PATENT OFFICE Washington, D.C. 20231 UNITEDSTATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 ,405 ,736October 15 1968 Trevor D. Reader et a1.

It is certified that error appears in the above identified patent andthat said Letters Patent are hereby corrected as shown below:

Column 8, line 22, "orifice" should read chamber Signed and sealed this3rd day of March 1970.

(SEAL) Attest:

Edward M. Fletcher, Jr.

Attesting Officer Commissioner of Patents WILLIAM E. SCHUYLER, JR.

1. A FLUID INVERTER COMPRISING; A BODY MEMBER HAVING A FLUID INTERACTIONCHAMBER DISPOSED THEREIN, SAID INTERACTION CHAMBER HAVING AN END WALL INWHICH A FLUID POWER NOZZLE IS DISPOSED, SAID FLUID POWER NOZZLE BEINGADAPTED WHEN SUBJECTED TO FLUID INPUT PRESSURE TO PROJECT A POWER JETTHROUGH THE INTERACTION CHAMBER, AN OUTPUT DUCT POSITIONED TO RECEIVETHE UNDEFLECTED POWER JET, SAID OUTPUT DUCT COMPRISING FIRST AND SECONDSPACED APART WALL MEMBERS LOCATED DOWN STREAM FROM THE POWER NOZZLE ANDON OPPOSITE SIDES OF THE AXIS OF THE POWER NOZZLE, A CONTROL SIGNALCHAMBER HAVING AN INPUT DUCT AT ONE END THEREOF FOR RECEIVING CONTROLFLUID INPUT SIGNALS AND A MOUTH PORTION AT THE OTHER END THEREOF WHICHOPENS INTO THE INTERACTION CHAMBER ON THE SAME SIDE OF THE POWER NOZZLEAS THE FIRST WALL MEMBER OF THE OUTPUT DUCT, THE SAID MOUTH PORTIONEXTENDING FROM THE POWER NOZZLE TO A POINT AT LEAST ONE THIRD THE LENGTHOF THE INTERACTION CHAMBER DOWNSTREAM FROM THE POWER NOZZLE, SAIDCONTROL SIGNALIS CHAMBER BEING OPERATIVE SO THAT WHEN A CONTROL FLUID ISAPPLIED THERETO A STATIC PRESSURE SIGNAL WILL EXIST AT SAID MOUTHPORTION THEREBY TO DEFLECT THE POWER JET AWAY FROM SAID OUTPUT DUCT, AVENT FOR SAID INTERACTION CHAMBER COMPRISING THE AREA BETWEEN THE SAIDEND WALL AND THE SECOND OF SAID WALL MEMBERS COMPRISING SAID OUTPUTDUCT, AND A DIVIDER BLOCK LOCATED IN THE SAME VENT DIVIDING SAID VENTINTO TWO UNLOADED VENT CHANNELS THE FIRST VENT CHANNEL OF WHICH ISDEFINED BY A FIRST SURFACE OF SAID DIVIDER BLOCK AND THE SAID END WALLAND THE SECOND VENT CHANNEL OF WHICH IS DEFINED BY A SECOND SURFACE OFSAID DIVIDER BLOCK AND THE SECOND OF SAID WALL MEMBERS OF SAID OUTPUTDUCT; THE SECOND VENT CHANNEL PROVIDING AN EXHAUST PATH FOR THE POWERJET WHEN IT IS DEFLECTED BY A SUITABLE PRESSURE APPLIED TO THE CONTROLCHAMBER, SAID SECOND SURFACE OF SAID DIVIDER BLOCK FORMING AN ACUTEANGLE WITH THE AXIS OF THE POWER JET AND BEING POSITIONED ANDDIMENSIONED TO PROVIDE A BOUNDARY LAYER ATTRACTION FORCE FOR THE POWERJET ONLY WHEN SAID POWER JET IS IN ITS DEFLECTED POSITION, AND SAIDFIRST VENT ACTING TO REDUCE THE BOUNDARY LAYER ATTRACTION FORCE OF THESECOND SURFACE OF SAID DIVIDER BLOCK SO THAT IT IT INSUFFICIENT TOMAINTAIN SAID POWER JET IN ITS DEFLECTED POSITION IN THE ABSENCE OF ASUITABLE CONTROL PRESSURE APPLIED TO SAID CONTROL ORIFICE.